From LAX, Delta and United offer connecting service (change of plane) to Jackson, Wyo. Restricted round-trip fares begin at $339. Jackson is about 56 miles south of Yellowstone.
For information on See Yellowstone Tours and snow coach excursions, go to http://www.seeyellowstone.com or call (800) 221-1151.
For information on West Yellowstone and other snow coach operators, go to http://www.westyellowstonechamber.com or call (406) 646-7701.
Yellowstone National Park, http://www.nps.gov/yell/index.htm.